In general, the processing of a color light-sensitive material essentially consists of a color developing step and a desilvering step. In the color developing step, silver halide which has been exposed to light is reduced by a color developing agent to produce silver. At the same time, the color developing agent which as been oxidized reacts with a color forming agent (coupler) to provide color images. The silver thus produced is oxidized by a bleaching agent in a subsequent desilvering step and then acted on by a fixing agent to become a soluble silver complex which is then dissolved and removed.
The practical developing process comprises various auxiliary steps besides the above described basic steps in order to maintain photographic and physical qualities of the images or improve the preservability of the images. Examples of such auxiliary steps include a hardening step, a stopping step, an image stabilizing step, and a washing step.
In recent years, the industry has seen a growing demand for rapid processing, i.e., shorter time required for processing, especially at the desilvering step, which accounts for the majority of the total processing time.
As bleaching agents there have generally been known red prussiate, bichromate, ferric chloride, ferric aminopolycarboxylate complex, and persulfate.
However, red prussiate and bichromate have a disadvantage in that these salts can give cyanide or hexavalent chromium pollution and thus require a special treatment facility. Ferric chloride has a disadvantage in that it produces iron hydroxide or stain at the subsequent washing process, thereby impeding the practical use thereof. Persulfate has a disadvantage in that it requires a remarkably long period of time to finish bleaching due to its very weak bleaching effect.
Ferric aminopolycarboxylate complex salts (particularly ferric ethylenediaminetetraacetate complex salts) have less pollution problems and no storage problem as for persulfate and are therefore most widely put into practical use as bleaching agents.
However, it cannot always be said that ferric aminopolycarboxylate has a sufficient bleaching capability.
As a means of expediting the desilvering process there has heretofore been known a combined blixing solution containing ferric aminopolycarboxylate and thiosulfate as described in West German Patent No. 866,605. However, such a combined blixing solution has a disadvantage in that the coexistence of a ferric aminopolycarboxylate complex, which has a weak oxidizing power (bleaching power), with a thiosulfate having a reducing power provides a much weaker bleaching power, making it extremely difficult to fully desilver a color light-sensitive material for photography having a high sensitivity and a high silver content, in particular.
Furthermore, if the processing is conducted with a reduced amount of replenisher of the processing solutions (i.e., bleaching solution, blixing solution and/or fixing solution) to be used in the desilvering of the silver halide color photographic material, in order to protect the environment, save costs, and simplify the processing, silver halide eluted from the light-sensitive material is accumulated in a high concentration as a silver complex in these processing solutions. This causes more precipitate to be produced or reduces the activity of the processing solutions, further weakening the bleaching power thereof. Thus, it was found that a reduction in the amount of replenisher of the processing solution to be used in the desilvering process causes many difficulties.
On the other hand, as a method of improving the bleaching power there has been proposed a method which comprises adding various bleaching accelerators to the bleaching bath, blixing bath, or previous bath (prebath) thereof. Examples of such bleaching accelerators include various mercapto compounds as described in U.S. Pat. No. 3,893,858, British Patent No. 1,138,842, and Japanese Patent Application (OPI) No. 141623/78 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), compounds containing disulfide bonds as described in Japanese Patent Application (OPI) No. 95630/78, thiazolidine derivatives as described in Japanese Patent Publication No. 9854/78, isothiourea derivatives as described in Japanese Patent Application (OPI) No. 94927/78, thiourea derivatives as described in Japanese Patent Application (OPI) No. 8506/70, and Japanese Patent Publication No. 26586/74, thioamide compounds as described in Japanese Patent Publication No. 42349/74, dithiocarbamate as described in Japanese Patent Application (OPI) No. 26506/80, and arylenediamine compounds as described in U.S. Pat. No. 4,552,834.
It is certain that among these bleaching agents, those showing a bleach accelerating effect are present. However, those bleaching accelerators leave much to be desired in practicality. For example, some bleaching accelerators are expensive or have insufficient stability in a bath having a bleaching capability.
Furthermore, if the light-sensitive material is processed in a bleaching bath, blixing bath, or prebath thereof containing these various bleaching accelerators, and these bleaching accelerators are compounds containing mercapto groups, these mercapto compounds produce a sparingly soluble silver salt with unexposed silver halide or silver halide produced by the bleaching reaction in the emulsion layer of the light-sensitive material. Such a sparingly soluble silver salt cannot be solubilized by a fixing agent, possibly causing poor fixation.
Thus, the inventors have found that the reduction of the amount of replenisher of the processing solution to be used in the desilvering process causes more silver ions to be accumulated in the desilvering bath, and these silver ions form a sparingly soluble silver salt with the mercapto compound, further reducing the bleach accelerating effect to an insufficient level. The inventors have also found that the presence of iodide ions in the desilvering solution promotes such a reaction.
Furthermore, the above described mercapto compounds include those which react with sulfite ions in the processing solution to undergo decomposition (Sulfur Dioxide, L. C. Schroeter, Pergamon Press (1966)). The ordinary blixing solution comprising a thiosulfate as a fixing agent contains a sulfite in combination. Therefore, such a mercapto compound is susceptible to decomposition in the blixing solution.
As described above, the use of such a mercapto bleaching accelerator in the processing solution or its prebath to be used in the desilvering process has many limitations.
On the other hand, there has been known a process which comprises processing a light-sensitive material containing such a mercapto compound or its precursor as described in Japanese Patent Application (OPI) Nos. 135834/87 and 80649/87. However, if such a mercapto compound is contained in a light-sensitive material, it may greatly affect the photographic properties, and silver halide contained in unexposed portions in the light-sensitive material and such a mercapto compound form a sparingly soluble salt. Thus, this approach leaves much to be desired.